Fix clippy::single_char_pattern

src/appservice_server.rs

@@ -25,7 +25,7 @@ where
 
     let mut parts = http_request.uri().clone().into_parts();
     let old_path_and_query = parts.path_and_query.unwrap().as_str().to_owned();
-    let symbol = if old_path_and_query.contains("?") {
+    let symbol = if old_path_and_query.contains('?') {
         "&"
     } else {
         "?"